(1) Field of the Invention
This invention relates to scanners, in particular to scanners for films.
(2) Description of the Related Art
A scanner for films generally has two modules: the light source module and the optical module. The light source module includes the light source and a carriage for the light source. The optical module is for processing the optical image signal and includes a frame and reflecting mirrors. In conventional scanners for slides, transparencies, photographic film negatives, X-ray films, etc., the light source module and the optical module are two separate entities. The light source module is fixed over the transparent scanning window and the protection window. The optical module is placed underneath the transparent scan window and the protection window. The protection window protects the light source and presses the film document against the scan window. The light source is mounted on the carriage and slides along a rail. The lowest point of the light source module must clear the protection window by a certain distance to allow for structural variations. A typical minimum clearance is 1.5 mm. Because of this 1.5 mm clearance, the light source cannot be in intimate contact with the protection window and the light source intensity is weakened.
FIG. 1 shows a prior art optical system of a scanner for films. A light source 10 is mounted on a base 12 which is attached to a carriage 17. The carriage can slide along a rail 14. The light source 10 emits a light beam 15 through a protection window 16 which is used to press a film document (not shown) against a scanning window 18. The light beam transmitted past the scanning window 18 is incident on an optical module 11, which has mirrors for further processing the optical signals. The base 12 has a light source 10 which is customarily softened with translucent glass placed underneath the base 12. The light beam emitted from the light source 10 passes through the protective window 16 to scan the film document placed over the scan window 18. The light beam now contains optical signals for incidence on the first mirror 13 of the optical module 11.
FIG. 2 shows another side view of FIG. 1. The carriage 17 supports a guide rod 14 on its right side and is attached to a module 12 for housing a light source 10 along its length. The carriage 17 slides along the guide 14. Underneath the light source module 12 is the protection window 16 and the scan window 18 on which a film document (not shown) is placed. Below the scan window 18 is the optical module 11.
FIG. 9 shows another prior art scanning system for film documents. The carriage 27 also functions as the support for the light source 10, which is hanging uncovered directly without a housing as shown in FIG. 10, and is capable for sliding along the guide rail 14. Underneath the protection window 26 is the scan window 18. The light beam 15 transmits through the protection window 26, the film document (not shown) and the scan window 18 to reach the optical module 11. The scan signal is reflected by the mirror 13 for further signal processing. The closest point between the lowest point of the light source 10 and the surface of the protection window 26 is indicated by the distance 284.
Due to manufacturing variations in either the structure of FIG. 1 or FIG. 9, the dimensions of different components may fluctuate somewhat. To allow for such fluctuations, the common practice is to provide a clearance 184 in FIG. 1 and 284 in FIG. 9 of at least 1.5 mm between the lowest point of the light source 10 and the protection window 16 to avoid rubbing the light source 10 against the protection window 16.
An object of this invention is to increase the light intensity of the scanner. Another object of this invention is to place the light source module as close to the optical module as possible. These objects are achieved by pushing the light source module against the optical module by means of spring action or by gravity. Separation between the light source module and the protection window pressing the document to be scanned is minimized to increase light intensity by inserting low friction material between the light source module and the protection window.